This research seeks to clarify the relationship between the chromosomal, protein and DNA topologies among the Felidae. Specifically, we are investigating the entire cat family using mitochondrial DNA (mtDNA) as an evolutionary probe in order to more finely resolve previous felid phylogenies. mtDNA has proven to be an excellent metric for elucidating evolutionary relationships because it is a rapidly evolving molecule that is entirely maternally inherited (i.e., the data are not confounded by meiotic events) and it affords a high degree of differentiation between closely related species. mtDNA has been extracted from several individuals in each of five target species: domestic cat, cheetah, clouded leopard, lion and Geoffrey's cat. mtDNA cleavage maps have been constructed for all target species using 17 restriction enzymes for an average of 43 sites per map. Intra- and interspecific variation has been calculated from these maps. The mtDNA of the domestic cat has been molecularly cloned into the pBR322 plasmid for use as a nick-translated probe in the "Southern" analysis of high molecular weight DNA from 35 of the 37 cat species. The resulting restriction fragment length patterns from this analysis are being used to construct a mtDNA phylogeny of the Felidae in toto. This dendrogram of evolutionary relationships will be compared to other topologies of the Felidae derived by other molecular and morphometric metrices.